1. Field of the Invention
The present invention relates to a display device, and more particularly, to a liquid crystal display (LCD).
2. Description of Related Art
Nowadays, the qualities the market demands from the thin film transistor liquid crystal display (TFT-LCD) are high contrast ratio, no gray scale inversion, low color shift, high luminance, full color, high color saturation, high responsive speed, wide viewing angle and the like. Currently, the technologies that meet the requirement of wide viewing angle include, for example, the twisted nematic (TN) LCD along with the wide viewing film, the in-plane switching (IPS) LCD, the fringe field switching LCD and a multi-domain vertically aligned (MVA) TFT-LCD.
Taking the conventional MVA-LCD panel as an example, since the alignment protrusions or slits formed on the color filter substrate or the TFT array substrate render the liquid crystal molecules arranged in multi-direction thereby obtaining a plurality of different aligned domains and thus meeting the requirement of wide viewing angle.
FIG. 1 is a diagram illustrating the relationship between the normalized transmittance and the gray level of a conventional MVA-LCD. Referring to FIG. 1, the abscissa is the gray level and the ordinate is the normalized transmittance. It is noted from FIG. 1 that although the conventional MVA-LCD panel can meet the requirement of the wide viewing angle, the transmittance-level curve has different curvatures as the viewing angle varies. In other words, when the viewing angle varies, the luminance displayed by the MVA-LCD changes, which in turn results in problems of color shift and color washout.
In order to solve the problem of color shift, several solutions have already been proposed one after the other. One of the solutions is adding one data line in a single pixel unit and disposing two pixel electrodes in the single pixel unit. Different data voltages are written to each of the pixel electrodes through different data lines in the single pixel unit. As a result, the two pixel electrodes of the single pixel unit provide different electrical fields and produce different arrangements of liquid crystal molecules so as to reduce the color shift. Although this solution mitigates the problem of color shift, however, the increased number of required data lines complicates the design of the driving circuit.
FIG. 2 is a schematic diagram of a conventional LCD. Referring to FIG. 2, an LCD 100 includes a driving signal generator 110, a look-up table (LUT) 120, a gate driver 130, a data driver 140, a drive voltage generator 150 and an LCD panel 160. As shown in FIG. 2, the driving signal generator 110 converts image data from the system into signals required by the data driver 140 and the gate driver 130. The look-up table (LUT) 120 is used for the image conversion process. The data driver 140 receives a data signal from the driving signal generator 110, generates a data voltage based on the driving voltage generator 150, and then inputs the display signal to the LCD panel 160. When the number of data lines doubles, the numbers of the data driver 140 and the look-up table 120 also double. The required capacity of the memory for the driver increases, which results in an increase in the production cost. Meanwhile, in the processing and transmission of signals, since the number of data lines increases, the driving signal generator 110 also needs to increase the number of signal lines and the bandwidth when outputting signals. Consequently, the driving circuit of the LCD 100 is rendered more and more complicated and prevents the production cost of the LCD 100 from being significantly lowered.